Free design for a canoe style boat.

[fishy1]

Basically, I'm looking to build a canoe, with two sets of rowlocks, so two people can row at once, but it should be possible to paddle as well. It should also be possible to mount a small (2hp) outboard on the back. I'm not planning to use it in the sea, but I will in large lochs where the waves can be choppy. I'd like it to be large enough to have two guys and kit and a little fuel tank. It'd also be brilliant if it was stable enough to fish in, and fairly light. I'm planning to build it out of stitch and glue. Is this a fairly suitable project for a novice? Also, would you recommend using marine ply and not epoxying it, or outdoor ply and expoying it, as outdoor ply is cheaper. I want to build something I can be pretty certain won't snap in half or spring a large leak when I'm a mile offshore and far from the nearest settlement.

Is there a design for something like this on the internet, or some plans I can modify? Any of you experts see any flaws in my plans? Many thanks

EDIT: Just realised this might have been better in the boatbuilding section. If so, I really am sorry. Feel free to move it.

[fishy1]

Anyone?

[lewisboats]

I hate to see someone not get an answer to a fairly easy question. There isn't much out there on rowing canoes...mostly they are changed in to wherrys and other such elegant craft. A simple stitch and glue boat would necessarily be a bit different. I took your criteria and came up with this sketch. It displaces 500 lbs or so or about 225 kilos and draws just under 4 inches or 10 cm, but should weight in at around 110 lbs or 50 kilos. It has a small transom to mount a small motor and has widely flaring sides to provide some increasing stability as the boat leans. One could stand while the other is seated or one could stand alone. Max beam is just over 4 ft 2 in or about 1.3 meters. Freeboard is 12" with depth of hull around 15"

Steve

Edited to add: it is 15 ft long and the parts should only have 1 joint in them, around the middle as they fit lengthwise into two sheets of ply layed end to end. You would probably need 4 sheets of 6 mm ply for the hull and another to fit it out with seats, air chambers, a small skeg, etc, along with some solid wood for the trim. I would recommend Marine ply AND epoxy to get maximum life out of the boat.

[fishy1]

Thank you so much, I'm really grateful.

[fishy1]

Is that epoxy the outer hull, or do interior as well? Do you have a rough guess how much I'd need to A) coat the hull and B) Do filletting, glass tape and everything else?

Also, you couldn't PM/email me a copy of those plans but in a higher resolution? It's just when I enlarge them I can't make out the writing. Cheers.

[tom28571]

Lewis's boat looks like a nice one. That said, it's difficult have a boat that rows and paddles well unless you add outriggers to a good narrow paddling boat. A compromise probably won't work all that well for either. If it's beamy enough for oarlocks on the gunwales, its too wide and awkward for a single paddler and vice versa.

No criticism of Lewis's boat, just an opinion.

[BWD]

The alternative, if you are open to it, is an outrigger canoe.
Selway Fisher has one for S/G I believe.
Gary Dierking has some for strip (more elegant), and ply on frame also.
Try http://homepages.paradise.net.nz/garyd/
Supposedly I am building something similar myself, although lately this has been a case of me staring at it...
Outriggers can go 8-10+ knots with a tiny outboard, paddle easily at 3-5 knots, and be made to be good for fishing. And they can take all sorts of interesting sailing rigs....
Not very Scottish though.

[fishy1]

I'm open to all alternatives.

I was kinda thinking I could build it with a wide transom, I.e 4ft wide so really no curve inward towards the back. Maybe this is a bad idea, I don't know. It would seem to give alot more space, and allow a good motor mount. Also it'd make it easier to trawl two rods out the back. It doesn't have to paddle well, just be paddlable so I could get silently up to wildlife.

Does anyone have a link to a site with an explanation of all the terms you use? It's just like when you say displacement is 225kg, does this mean to load it up to just before it sank, it would need 225kg of ballast? If so, is this not rather close to the weight of two guys, oars, fishing stuff and a small engine?


An outrigger would be good it's just I always have an image of shearing it off on a wave (a big lever) and then the craft being basically unrowable. When I think about it, I could make the outrigger out of wood and have two beams connecting it to the canoe and have it run across so you'd sit on it.

[BWD]

When folks say displacement, they can mean a lot of things. But is defined as the weight of water the boat pushed out of the way when floated. Or the weight of water that overflowed from Archimedes's tub when he got in, some years ago....
So, the 225kg would refer to the weight (mass) of the boat plus everything in it, identical to the 225 kg of water it would displace when put in a lake, etc.
Usually the displacement means the weight of the boat plus all it is designed to hold. At this weight the boat floats (we hope). And even better, we hope it floats on its DWL or (DesignedWaterLine)

For most boats it takes a lot more to swamp, but their performance and safety factors for strength stability etc. decline above the intended max. or "heavy" displacement.
If it's not this type of displacement a designer (or whoever) refers to it is usually the dry weight of the boat itself rigged for use, without people, stores, fuel etc. aboard. And usually it is referred to as "dry weight."
For bigger boats sometimes "lightship" displacement is given. For ships this no doubt has a very specific meaning including certain equipment and some fraction of fuel, water tankage, etc.
For us in the recreational world it means something more like, the reason your boat is so slow (or sank, ran out of gas, etc.) is because you put all that junk on board, so it weighs too much...

Anyway, an outrigger may or may not be to your liking.
As you have figured out, the beams between the main and outrigger hulls have to be strong. Back to displacement, part of your concern about different forces on the two hulls is addressed by the different sizes, shapes and displacements of the two hulls. The little one, if pressed too hard, will simply submerge for a moment, and then pop back up. This reduces the force applied to the other hull, so hopefully nothing breaks. The little hull (ama) also usually has a shape to help this process out, like a torpedo shape, or at least a highly crowned deck so water will roll right off it. That's an outrigger.

But if you really want a rowboat, an outrigger probably won't make you happy.

[fishy1]

And I take it you could easily calculate the DWL if you know it's volume at all heights, and it's displacement?

[lewisboats]

The DWL is simply the length of the waterline at the design draft of the hull. It sounds like you are looking more for a skiff than a canoe. Most skiffs can be paddled but arent designed specifically for it. Try looking at these plans:

http://www.duckworksbbs.com/plans/lewis/duckskiff/index.htm

The rowing version could easily use a small motor to putt around.

Steve

[fishy1]

Is there any reason structurally why boats only ever have space for one to row? It's just it would be good if two could row, I take it I just move seats around and add two rowlocks?

[lewisboats]

No...and there are many examples of multiple station rowing boats...from Skulls to Trireames (SP?). However...most small boats in the category you are looking for are usually manned by one rower with one or two passengers. Rowing stations are thus designed for solo or with passenger rowing but not with two rowing at the same time. The first design that I showed did allow for two rowers...one at the 1/3 position (aftmost seat) and one at the 2/3 position, (forwardmost seat). A center seat could be accomodated for a single rower, but would probably need to be made removable so that the forwardmost rower had leg room to row when rowing double. With outriggers, most oar lengths can be used with a medium beam such as was presented in the first design. If you need a wider transom I could fit that in but it would be more difficult to row and not as easy on gas as the initial hull form, however...it would indeed support more weight aft and more approximate a skiff design. The double ended design presents an easily driven, hydrodynamic hull to the water while at the same time the tombstone transom allows the mounting of a small outboard to provide maximum displacement speed, including the use of electric motors. A small motor will drive the boat to hull speed with the minimum of fuss and still allow a rower or rowers to also manage a good speed from the hull while at the same time allowing a decent amount of kit to be carried. Don't underestimate the value of a double ended boat... time has proven that they have a large place in efficient movement of people and cargo

Steve

[tom28571]

There is another reason for more than one rowing station in small boats. How many times have you seen a small dinghy being rowed across a harbor with the passenger sitting on the stern seat and the bow sticking up a foot in the air and the stern almost submerged. The poor rower has no idea where he is going and little ability to steer to get there. A second set of oarlocks and another seat or, better yet, a movable seat will allow the boat to be balanced on its lines with any number of passengers or load.

[fishy1]

What program are you guys using to generate the green designs of boats I keep seeing, and where can you get it? Just seems like a pretty useful tool.

[Guest625101138]

What program are you guys using to generate the green designs of boats I keep seeing, and where can you get it? Just seems like a pretty useful tool.

It is called DelftShip. There is a free version here:
http://www.delftship.net/
Log in and download it. It will be the best 5 minutes you will spend if you have an interest in boats.

I have attached an fbm file of a boat that sort of matches your needs. This can be opened with Delftship. It is a good place to start if you want to design your own. It would be suitable for stich and glue. It would only need to be glassed on the outside and in the cockpit as the hull is self bailing with the cockpit. The enclosed sections give good structural rigidity even with light sheeting.

You can produce sheet developments using Delftship. Takes a bit of work but much faster than laying sheets over a frame.

The boat has not been built but it will perform well. It is not super stable but fine for sitting and OK for standing if careful. You could make it wider but this will reduce performance somewhat. Depends on what ballance you want to strike between speed and stability. It could be lengthened if you want two rowing positions.

Rick W.

[Gilbert]

I don't think anyone mentioned that a second pair or oars is a significant expense in a small boat and they also take up room when not in use.

[fishy1]

But when not in use, the oars don't need to be taken along. Price of 2 oars is not much compared to total price of boat.

[kengrome]

I have attached an fbm file of a boat that sort of matches your needs. It would be suitable for stitch and glue.Rick, how refined is this hull shape? Have you run it through michlet / godzilla or is this just a starting point?

I downloaded your .fbm file and made the layer transparent, turned on the station visibility, and took a look at it more carefully. It seems this would be a very easy boat to build by carving the shape out of a big foam block, then covering the whole thing with epoxy and glass to create a monocoque structure -- kind of like a "surfboard canoe" or maybe a "surfboard rowboat" ... or a "sit-on-top rowboat" perhaps?

:)

The transom should be wood for the outboard of course. Wooden gunwales pre-drilled for oarlocks every 6 inches (and glassed into the hull) might be an ideal way to provide both multiple and adjustable rowing stations, too. My thought here would be to use full length bowstem to transom wooden gunwale logs and glass them into the hull to add longitudinal strength to the hull, even though the added strength probably wouldn't be necessary.

What do you think about this type of construction?

[Guest625101138]

Ken
It is a Godzilla optimised shape for a transom and stability criteria suitable to stand in (with care) - KMT = 0.6m. I cannot remember the design speed but it will do 4.6kts with 100W into an efficient prop or maybe with 120W using paddles.

It has rounded edges for glass moulding over foam but could also have hard edges for stitch and glue. As it is, it was designed for total displacement of 120kg. Would need to be increased in volume a bit to carry two.

Polystyrene foam is OK but you need to use epoxy resin with this. I find polyurethane foam too flexible for long hulls but if it was solid or with plenty of ribbing it would be adequate as well - a timber keel and timber gunwale as you suggest would help keep the shape during layup. Polyurethane foam with three layers of 200g/sq.m should be a nice strong boat. You might want to lift the transom a bit for an outboard.

Rick W.